This Week's Air Quality Is Worst On Record For San Francisco Bay Area

Air pollution in counties of the San Francisco Bay Area this week has been the worst since 1999 when officials began collecting data.

"The pollution is so high it's comparable to high pollution days in China," says Lisa Fasano at the Bay Area Air Quality Management District.

The worst hour so far was measured on Tuesday in Napa, Calif., with an Air Quality Index of 404 for small particulate matter — so high it's off the chart, as you can see below.

Officials warn that very fine smoke particles, a fraction of the size of a human hair, can lodge in the lungs and, particularly in some vulnerable populations, do damage.

"When we breathe particulates, they bypass the lung system and get into our bloodstream," says Fasano. "They exacerbate respiratory conditions like asthma, [chronic obstructive pulmonary disease], emphysema and other conditions, because they are very harmful."

A seasonal inversion layer is putting a lid on the pollution and holding it in the region. Usually the Bay Area benefits from a natural air conditioning system with winds blowing in off the coast and carrying the air inland.

Residents in the North Bay are experiencing the brunt of the pollution because of nearby wildfires in California's wine country. Residents in Napa, Solano and Sonoma counties should try to stay inside buildings with air conditioning. But people in the East Bay and South Bay are not completely in the clear because the toxic air is creeping all over the region. You can look up your ZIP code here and find a five-day forecast here.

"We are also seeing elevated levels in San Francisco and Redwood City," says Fasano. "We are all being impacted by this really unhealthy air pollution."

Fasano recommends buying a face mask at the hardware store with an N-95 rating or higher. Unfortunately neither a hospital mask nor a bandanna tied over the face prevents noxious air from entering the lungs, and to make much of a difference, even N-95 masks must fit well. Fasano suggests staying inside as much as possible while skies are smoky to avoid breathing both particle pollution and ash wafting through the air.

Call your doctor if you have particular concerns about your own health or that of a family member. And follow these precautions to help protect your health if you're feeling symptoms or if the air in your region is worse than "moderate" as defined in the chart above:

Minimize outdoor activities

Stay indoors with windows and doors closed

Do not run fans drawing smoky air inside. Run your air conditioner only if it does not bring smoke in from the outdoors

Consider, in some cases, leaving the region until air quality improves.

This post is based on a story by KQED that is being periodically updated with the most recent air quality numbers.

Much of Northern California is under thick, black smoke because of the wildfires. The worst of it is in Napa and Sonoma counties. And it's being blown south into the San Francisco Bay Area, where people are now breathing the most polluted air on record. Member station KQED's Lesley McClurg reports.

LESLEY MCCLURG, BYLINE: On a street corner in San Francisco, cyclists whiz by me wearing white surgical masks, and a woman here is approaching me with a turquoise mask on.

MEGAN BEAN: I have been wearing it in my car, to walk around. Even just a few minutes without it sometimes starts me coughing and makes my throat burn.

MCCLURG: Megan Bean's mask is tightly pressed to her face to protect her from the air that smells like a campfire.

MCCLURG: The sky is an eerie orange with thick, low clouds. In parts of the city, it's tough to see through the haze at street level. Lisa Fasano monitors pollution for the Bay Area Air Quality Management District.

LISA FASANO: It's very unhealthy. We're seeing levels that rival that that you might see in China on poor air quality days.

MCCLURG: Usually San Francisco benefits from a natural air conditioning system. Winds blow in off the coast and sweep air out of the city. But Fasano says an inversion layer is locking in the smoke from all the wildfires.

FASANO: We are seeing readings that are really off the charts. It's very, very unhealthy.

MCCLURG: The levels are record-breaking. The worst part is you can't even see the stuff that's really bad for you. Very fine toxic particles are wafting through the air. When you breathe them in, they go through your lungs. And Fasano says they can go directly into your bloodstream.

FASANO: They can trigger asthma attacks. They can exacerbate emphysema problems. They can in fact produce heart attacks.

MCCLURG: Vulnerable populations like older people and young kids are at the highest risk. That's why many schools are closed. Dr. Robert Blount is a pulmonologist at UC San Francisco.

ROBERT BLOUNT: Children have developing organs that are increasingly susceptible. They also tend to breathe faster than adults and tend to be more active outside.

MCCLURG: Blount says it's normal to experience stinging eyes, an itchy throat or even headaches in this kind of pollution. He says anyone struggling to breathe or feeling tightness in their chest should seek medical treatment. Everyone should stay inside as much as possible.

BLOUNT: Closing the windows and, if there is an air conditioner, turning on the air conditioner to recirculate the air inside and filter the air from the outside.

MCCLURG: Resident Megan Bean plans to keep her turquoise mask on at home in the East Bay this weekend. She says her commute this week to San Francisco was grim.

BEAN: Driving over the bridge, I couldn't see the city. I couldn't see the Golden Gate Bridge. It's scary.

MCCLURG: The air may stay like this for a while. High winds are in the forecast near the largest fires tonight, and no rain is in sight. For NPR News, I'm Lesley McClurg in San Francisco. Transcript provided by NPR, Copyright NPR.